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Newswise — WASHINGTON – People who think they’re less active than others their age have a greater chance of dying younger than people who perceive themselves as more active, even if their actual activity levels are the same, according to research published by the American Psychological Association.

People who believed they weren’t as active as their peers were 71 percent more likely to die during the study’s follow-up period than were people who believed they had a more active lifestyle, the study said. This result remained even after controlling for actual amounts of activity, chronic illnesses, age and other demographic and health factors.

Stanford University researchers Octavia Zahrt, PhD, and Alia Crum analyzed data from three nationally representative samples with a total sample size of 61,141 U.S. adults. The participants were surveyed between 1990 and 2006 and mortality data on all participants were collected in 2011. The findings are published in the APA journal Health Psychology.

“Most people know that not exercising enough is bad for your health,” said Zahrt, a doctoral candidate at the Stanford University Graduate School of Business. “But most people do not know that thinking you are not exercising enough can also harm your health.”

Participants answered a variety of questions about their level of activity. In two of the samples, actual physical activity was determined via self-reports, where the participants indicated the types of activities they had done in the recent past, including frequency, duration and intensity. In the other sample, participants wore a device called an accelerometer that measured their real-time activity levels for a week. In addition, participants reported their perceived level of physical activity by answering the question, “Would you say that you are physically more active, less active, or about as active as other persons your age?”

Interestingly, participants’ perceptions about physical activity did not closely mirror their actual activity levels. “Our perceptions about how much exercise we are getting and whether or not we think that exercise is adequate are influenced by many factors other than how much exercise we are actually getting,” said Zahrt. “For example, if you live in an area where most of your peers are really fit, you might perceive yourself as relatively inactive, even though your exercise may be sufficient. Or if you believe that only running or working out at the gym count as real exercise, you may overlook the exercise you are getting at work or at home cleaning and carrying kids around.”

Participants also reported their gender, age, race/ethnicity, marital status, education, employment, annual household income, access to medical care and other demographic data. In addition, participants rated their general health on a scale of 1 (excellent) to 5 (poor), and gave a detailed medical history, which helped researchers determine each person’s risk for disease and premature mortality. Disability, mental health and body mass index were also measured. All of these variables were statistically accounted for in the analyses showing that perceptions about physical activity significantly correlated with mortality.

How do perceptions have such powerful effects? There are several possible pathways, according to the authors. One pathway is the placebo effect: many research studies show that active drugs are less effective if we don’t know that we have taken them. “Following this logic, someone who does not believe that she is exercising enough may get fewer physiological benefits from activity than someone who believes she is exercising enough,” said Crum, assistant professor of psychology and director of the Mind and Body Lab at Stanford University. “Placebo effects are very robust in medicine, it is only logical to expect that they would play a role in shaping the benefits of behavioral health as well.”

Another pathway is that when people perceive that they are doing worse than their peers, they become depressed, fearful and less active, according to the authors. These experiences, in turn, can worsen health.

In this study, Zahrt and Crum did not test which of these mechanisms might be at work. They also did not prove that participants’ perceptions about their physical activity caused the observed differences in life expectancy, as correlation does not mean causation. Nevertheless, other experiments from their lab do support the idea that mindsets directly affect behavior and health.

“Many Americans think that the only healthy physical activity is vigorous exercise in a gym or on a track,” Crum noted. “Our research suggests that perceiving everyday activities as good exercise is almost as important as doing the activities in the first place. In the pursuit of health and longevity, it is important not only to adopt healthy behaviors but also healthy thoughts.”

The American Psychological Association, in Washington, D.C., is thelargest scientific and professional organization representing psychology in the United States. APA's membership includes nearly 115,700 researchers, educators, clinicians, consultants and students. Through its divisions in 54 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance the creation, communication and application of psychological knowledge to benefit society and improve people's lives.